gaps.md §4 carried two evidence paragraphs, an older one saying PRs #158
and #161 were open and a newer one saying all 2-D kinds survive XLSX round
trip, both repeating the resize, smooth-line, Switch Row/Column and
trendline statements. It is one paragraph with the current status again.
The Mainstream chart row in target-app-parity.md listed trendlines as
missing; they are read, written and drawn (`Series::trendlines`, the XLSX
chart reader and writer, `chart.addElement`), as chart-parity.md records.
The row now says so and keeps "no axis options". No score change.